Internal combustion engines may be used in a variety of applications such as, for example, passenger and industrial vehicles, marine, stationary and aerospace applications. There are generally two dominant ignition cycles, which are commonly referred to as gas and diesel cycles, or more formally as spark ignited (SI) and compression ignition (CI) cycles, respectively.
Exhaust-driven turbochargers may be used to improve the power output and overall efficiency of an internal combustion engine. Specifically, exhaust gas energy may be used to drive a turbine. The turbocharger includes a compressor and a turbine, where the compressor is mounted on a shaft of the turbocharger, opposite the turbine. The turbine converts engine exhaust gas into mechanical energy, which is used to drive the compressor. The compressor draws in and compresses air. The compressed air is then directed to an intake manifold of the internal combustion engine.
A relief valve, such as a compressor discharge valve or a blow-off valve, may be mounted on an intake pipe located downstream of the turbocharger before a throttle. Specifically, a compressor discharge valve may be used to vent compressed air back into an inlet of the compressor. A blow-off valve is similar to a compressor recirculation valve, but vents to the atmosphere rather than back to the inlet of the compressor. The relief valve may be used to alleviate a sudden surge or spike in pressure that may occur when the throttle closes (i.e., when an operator suddenly lifts his or her foot off of the gas pedal and the throttle closes).
Air compression systems have been used on semi-trucks and other types of commercial vehicles in order to power air brakes. The air compression system may include an air compressor that is used to supply compressed air to a storage tank. The air compressor may be powered by a crankshaft pulley, or by timing gears of the internal combustion engine. The compressed air in the storage tank may be used for the air brakes. In addition to the air brakes, the compressed air may also be used to actuate the relief valve (i.e., the compressor discharge or blow-off valve). Specifically, a vacuum pump may allow the compressed air in the storage tank to selectively flow to the relief valve. The vacuum pump may be driven by an electric motor, or by the crankshaft or other rotatable shaft of the internal combustion engine. However, the vacuum pump may add significant cost and complexity to the system. Accordingly, there exists a need in the art for a simpler, cost-effective approach to actuate a relief valve in a turbocharger system, especially in semi-trucks and other types of commercial vehicles.